Hot Water Heating
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Q: At max cruising speed my engine starts to overheat. When I back off the throttle the temp quickly returns to normal. I thought it was the heat exchanger and I bought a new one but did not replace it yet. However, this weekend I noticed that the hot water from the water heater was not heating up. The best it would get is lukewarm and that was after running the engine for 75 minutes. My question is do you think I have a thermostat problem? Has anyone else had problems with the water heater?
- Had the same over-heating problem on HARD TIMES last year: problem went away when I changed the water pump out. I didn't pay any attention to the water heater performance, however. I suppose reduced water flow from a failing pump/impeller could give poor flow though the water heater, and hence slow heating. Replace the raw water impeller and see if the other problem takes care of itself. John Nixon
- We had a similiar problem where the temp would start to creep up when the engine was run at cruising speed. When we slowed down, the temp would go back to normal. We fixed our problem by replacing the raw water pump. The bearing on the raw water pump wallered out the pump housing so we had to replace the whole pump. We had a different problem with the fresh water. Our cold water side was even getting warm. After replacing the pump - the cold water side was cold. We had a problem with an air lock but the temp would climb at the dock. I checked my thermostat by placing it in a pan of water with a meat thermometer on the stove. I heated the water and watched - at 160 degrees - the thermstat popped open. Joe & Pat Turner, Lovepat #1039
- Check the rubber water pump impeller, If it has been a while since changed it may have taken a "set". of it may be soft and the vanes are flexing to much at higher RPMs, sort of like cavitating, the vanes bend back and if too soft will bend or flex to much. these impellers are not positive in that the faster they go the more water the move, not so, if you have winterized with the non toxit (red or pink ) antifrieze the impeller has most likly softened. You should replace the impeller once a year if using the red stuff, two years at most, for standard antifreeze. Dave, Nonsense #713
- We had the same problem. It turned out there was no gasket installed on he raw water pump cover. The $1.63 paper gasket did the trick. Of course, I'd already removed and checked the heat exchanger - it was clean as a baby's bottom!!! How are your hoses, both to the hot water heater and to the exchanger? Al Watson found a kink in the hose going to the exhaust muffler and replaced that to solve some overheating on his boat. John Coulthard's impeller idea also has merit. Stu Jackson, Aquavite #224
- Does it overheat a little or a lot? On our boat we had a slight overheating at higher rpm - noticeable only because the temperature typically holds so well. It was the water pump impeller. You didn't mention if you did this so please forgive me if I am stating the obvious. Check to make sure the raw water intake is clear. If something restricts the raw water intake a little bit, my experience suggests that it won't overheat until the rpm gets up there and then overheats quite a bit. What I do, when I am suspicious, is to turn off the motor and take off the raw water intake filter. The raw water should flow freely with a reasonable volume. The filter should be clear. Once you have done this with what you know is a clear raw water inlet you will know what to look for. If I am still suspicious then I run a flexible wire back down the valve and wiggle it up and down. If the volume of water increases, or changes in any way for that matter, there is definitely a problem and I would go overboard to check it from the outside (burrrr!). Usually it is a bit of weed. We sucked up a plastic bag once - the temperature really took off - you *know* when this happens :-). In your case I'd just be looking for a bit of weed or something sucked part way in, or possibly marine growth if it has been a long time since the bottom has been done. John
